Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$56.36	5.555%	$59.4908	$59.49	$59.50	$59.50
Purchase #2	$62.89	13.286%	$71.2456	$71.25	$71.25	$71.20
Purchase #3	$152.91	10.335%	$168.7132	$168.71	$168.70	$168.70
Purchase #4	$34.97	5.393%	$36.8559	$36.86	$36.85	$36.90
Purchase #5	$200.46	7.567%	$215.6288	$215.63	$215.65	$215.60
Purchase #6	$86.45	13.769%	$98.3533	$98.35	$98.35	$98.40
Purchase #7	$77.43	7.332%	$83.1072	$83.11	$83.10	$83.10
7 purchase totals =	$671.47		$733.3948	$733.40	$733.40	$733.40